This invention relates to the Armstrong Process as described in U.S. Pat. Nos. 5,779,761, 5,958,106 and 6,409,797, the disclosures of each of which is incorporated herein by reference. When the above-captioned patents were filed, it was understood that the steady state reaction temperature could be varied depending upon the amount of excess liquid metal or the ratio of liquid metal to halide being reduced. For instance, the above-identified patents taught that using a greater excess of the liquid metal beyond the stoichiometric amount required for the reaction would produce a lower steady state reaction temperature and similarly, diluting or reducing the amount of halide introduced into the liquid metal would also reduce the steady state operating temperature of the process. However, there was no appreciation of the nature of what occurred at the reaction zone, as separate from down stream conditioning, and no appreciation that the particle size of the powder produced could be controlled by manipulating various parameters in the reaction zone.
Although the above referenced patents disclose that powder is produced having average size distributions in the range of from about 0.1 micron to about 10 microns, in fact what was produced was not controllable but was whatever happened to be produced according to the parameters of the reaction. Powder morphology has been discovered to be an important factor in the production of powder. Moreover, larger diameter powders have larger packing fractions and the control of the powder morphology has become an important aspect in the development of the Armstrong Process. It has been discovered that powder morphology is affected by a number of parameters including the temperature of the reaction zone, the length of time that the material stays in the reaction zone.